1. Field of the Invention
This invention relates to pressure sensitive copying systems, and more particularly to a process for the production of a manifold carbonless form and to the carbonless form itself.
2. Prior Art
Manifold forms for commercial and private use have been in common use for several years. Historically, the standard business form has taken a variety of shapes. The most common is a multiple part form with sheets of carbon paper being insertable between the various sheets. This concept is very cumbersome as the carbon paper had to be both inserted, removed and disposed of in addition to the deficiencies commonly noted in the use of carbon paper such as smudging. In response to the obvious problems a form was developed having the carbon paper already inserted between the various sheets making up the form and being available for easy removal and disposal. This removal and disposal was made even more convenient by the attachment of the carbon paper together at one edge, generally the bottom, so that by merely ripping out the bottommost edge of the form all of the carbon paper would be removed. This system has been and still is being used by many retail department stores. All of these systems have historically suffered from one common deficiency, namely the use of carbon paper. Carbon paper, while adequate for some image transfer purposes is not a preferred product as it is very cumbersome to work with, it is very messy and in general does not form the quality image which is desired. In addition, as is commonly encountered with the use of carbon paper the more sheets of carbon paper that are used the fainter the image on the last sheets of the form. This is especially true where more than three to four sheets per form are used. Examples of patents relating generally to the use and manufacture of carbon paper and other image transfer systems containing dyes and pigments are:
U.s. pat. No. 2,299,694 (1942) to Green PA1 U.s. pat. No. 2,374,862 (1945) to Green PA1 U.s. pat. No. 3,016,308 (1962) to Macauley PA1 U.s. pat. No. 3,020,170 (1962) to Macauley PA1 U.s. pat. No. 3,079,351 (1963) to Staneslow et al PA1 U.s. pat. No. 2,712,507 (1955) to Green PA1 U.s. pat. No. 2,730,456 (1956) to Green et al PA1 U.s. pat. No. 3,914,511 (1975) to Vassiliades
In recognition of the deficiences of carbon paper as an image transfer media a variety of new products have been introduced into the marketplace. One such product is commonly referred to as carbonless paper. Carbonless paper, briefly stated, is a standard type of paper wherein during manufacture the backside of the paper substrate is coated with what is referred to as a CB coating, the CB coating containing one or more color precursors generally in capsular form. At the same time the front side of the paper substrate is coated during manufacture with what is referred to as a CF coating, which containes one or more color developers. Both the color precursor and the color developer remain in the coating compositions on the respective back and front surfaces of the paper in colorless form. This is true until the CB and CF coatings are brought into abutting relationship and sufficient pressure, as by a typewriter, is applied to rupture the CB coating to release the color precursor. At this time the color precursor contacts the CF coating and reacts with the color developer therein to form an image. Thus the image from the top sheet is transferred to the next sheet without the use of carbon paper. Carbonless paper has proved to be an exceptionally valuable image transfer media for a variety of reasons only one of which is the fact that until a CB coating is placed next to a CF coating both the CB and the CF substrates are in an inactive state as the co-reactive elements are not in contact with one another. Patents relating to carbonless paper products are:
A third generation product which is in an advanced stage of development and commercialization at this time and which is available in some business sectors is referred to as self-contained paper. Very generally stated self-contained paper refers to an image transfer system wherein only one side of the paper needs to be coated and the one coating contains both the color precursor, generally in encapsulated form, and the color developer. Thus when pressure is applied, again as by a typewriter or other writing instrument, the color precursor capsule is ruptured and reacts with the surrounding color developer to form an image. Both the carbonless paper image transfer system and the self-contained transfer system have been the subject of a great deal of patent activity. A typical autogeneous record material system, earlier sometimes referred to as "self-contained" because all elements for making a mark are in a single sheet, is disclosed in U.S. Pat. No. 2,730,457 (1956) to Green.
A disadvantage of coated paper products such as carbonless and self-contained stems from the necessity of applying a liquid coating composition containing the color forming ingredients during the manufacturing process. In the application of such coatings volatile solvents are sometimes used which then in turn requires evaporation of excess solvent to dry the coating thus producing volatile solvent vapors. An alternate method of coating involves the application of the color forming ingredients in an aqueous slurry, again requiring removal of excess water by drying. Both methods suffer from serious disadvantages. In particular the solvent coating method necessarily involves the production of generally volatile solvent vapors creating both a health and a fire hazard in the surrounding environment. In addition, when using an aqueous solvent system the water must be evaporated which involves the expenditure of significant amounts of energy. Further, the necessity of a drying step requires the use of complex and expensive apparatus to continuously dry a substrate which has been coated with an aqueous coating compound. A separate but related problem involves the disposal of polluted water. The application of heat not only is expensive, making the total paper manufacturing operation less cost effective, but also is potentially damaging to the color forming ingredients which are generally coated onto the paper substrate during manufacture. High degrees of temperature in the drying step require specific formulation of wall-forming compounds which permit the use of excess heat. The problems encountered in the actual coating step are generally attributable to the necessity for a heated drying step following the coating operation.
The drying step involving solvent evaporation and/or water evaporation and the input of heat does not permit the most economic and efficient manufacture of manifold forms. In addition to the drying step which hinders manifold form production the necessity for the application of heat for solvent evaporation is a serious disadvantage since aqueous and other liquid coatings require that special grades of generally more expensive paper be employed and even these often result in buckling, distortion or warping of the paper since water and other liquids tend to strike through or penetrate the paper substrate. Additionally, aqueous coatings and some solvent coatings are generally not suitable for spot application or application to limited areas of one side of a sheet of paper. They are generally suitable only for application to the entire surface area of a sheet to produce a continuous coating. Patents considered relevant to this concept are:
Canadian Patent 945,443 (1974) to Busch.
Another problem which has been commonly encountered in attempts to continuously manufacture manifold forms has been the fact that a paper manufacturer must design paper from a strength and durability standpoint to be adequate for use in a large variety of printing and finishing machines. This requires a paper manufacturer to evaluate the coating apparatus of the forms manufacturers he supplies in order that the paper can be designed to accommodate the apparatus and process designed exhibiting the most demanding conditions. Because of this, a higher long wood fiber to short wood fiber ratio must be used by the paper manufacturer than is necessary for most coating, printing or finishing machines in order to achieve a proper high level of strength in his finished paper product. This makes the final sheet product more expensive as the long fiber is generally more expensive than a short fiber. In essence, the separation of paper manufacturer from forms manufacturer, which is now common, requires that the paper manufacturer overdesign his final product for a variety of machines, instead of specifically designing the paper product for known machine conditions.
By combining the manufacturing, printing and finishing operations into a single manufacturing facility a number of advantages are achieved. First, the paper can be made using ground wood and a lower long fiber to short fiber ratio as was developed supra. This is a cost and potentially a quality improvement in the final paper product. A second advantage which can be derived from a combination of manufacturing, printing and finishing is that waste or re-cycled paper hereinafter sometimes referred to as "broke" can be used in the manufacture of the paper since the quality of the paper is not of an overdesigned high standard. Third and most importantly, several steps in the normal process of the manufacture of forms can be completely eliminated. Specifically drying steps can be eliminated by using a non-aqueous, solvent-free coating system and in addition several warehousing and shipping steps can be avoided thus resulting in a more cost efficient product.
Additionally, by using appropriate coating methods, namely non-aqueous, solvent-free coating compositions and methods, and by combining the necessary manufacturing and printing steps, spot printing and spot coating can be realized. Both of these represent a significant cost savings but nevertheless one which is not generally available when aqueous or solvent coatings are used or where the manufacture, printing and finishing of paper are performed at geographically separated manufacturing facilities. An additional advantage of the use of solvent-free, non-aqueous coating compositions and the combination of paper manufacturer, printer and finisher is that when the option of printing followed by coating is available significant cost advantages occur. More particularly, by printing prior to coating from about 10% to about 30% fewer capsulated color forming ingredients need to be used to achieve the same satisfactory levels of image transferability. This advantage is realized because when the paper is transferred to a forms manufacturer in coated form the paper of necessity will lose some of its capsulated color formers when printed because of the pressure rupturability of the material. This disadvantage is eliminated when the paper is printed first followed by coating.
Many of the particular advantages of the process and product of this invention are derived from the fact that a non-aqueous, solvent-free coating composition is used to coat the paper substrate. This is in contrast to the coatings used by the prior art which have generally required an aqueous or solvent coating. For purposes of this application the term "100% solids coating" will sometimes be used to describe the coating operation and should be understood to refer to the fact that a non-aqueous, solvent-free coating composition is used and therefore the normal drying step normally present in the manufacture of paper and in coating has been eliminated.